JP2588772B2 - Method of thermal cracking residual hydrocarbon oil - Google Patents

Abstract

Process for thermal cracking of residual hydrocarbon oils by 1) feeding the oil (1)(2) and a synthesis gas (14) to a thermal cracking zone (3), the gas having a temperature sufficiently high to maintain the temperature in the cracking zone (3) by means of direct heat exchange at 420-850 DEG C, 2) separating the cracked products into (a) a gas (5), (b) one or more distillates and (c) a cracked residue (6), 3) separating the cracked residue (6) into one or more heavy hydrocarbon oils poor in asphaltenes (18) and one or more heavy hydrocarbon oils rich in asphaltenes (18), 4) gasifying (19) the oil(s) rich in asphaltenes (18) in the presence of oxygen and steam to produce synthesis gas (21), and 5) applying synthesis gas from step (4)(21) as synthesis gas in step (1) (4).

Description

The present invention relates to a method for thermally cracking residual hydrocarbon oils.

BACKGROUND OF THE INVENTION Residual hydrocarbon oils can be obtained by distilling crude mineral oils at atmospheric pressure to produce a straight distillate fraction and a residual oil, also called "long residue". The long residue is distilled, usually at sub-atmospheric pressure, to produce one or more so-called "vacuum distillates" and residual oils, also called "short residues". Both the above-mentioned residual oils and other residual oils (such as those obtained from tar sands and shale oils) have been the subject of much research aimed at conversion to more valuable products.

"" Science and Technology, Petroleum and Petroleum-Natural Gas-Petrochemistry in Relation to Fuel Chemistry (Wissenschaft und Technik, Erdoel
und Kohle-Erdgas-Petrochemievereinigt mit Brenns
toff-Chemie), 36 , October 1983, pp. 457-461 relates to the thermal cracking of residual hydrocarbon oils in the presence of hydrogen. In this manner, tar sands heavy oil (heavy oil obtained from tar sands) is cracked to produce cracked products, and from these cracked products, carbonized with 1 to 4 carbon atoms per molecule. A gaseous fraction containing hydrogen and a liquid residual fraction are separated. The liquid residual fraction was a 70% by weight distillate (final boiling point 59%).
2 ° C). The experiments involved preheating the tar sands heavy oil to a temperature of 375 ° C. and hydrogen to a temperature of 1200 ° C. and introducing these preheated materials to the reaction vessel (the temperature of the hydrogen High enough to provide the necessary heat.)

Japanese Patent Application Publication No. 96589/1987 discloses that a mixture of heavy hydrocarbon oil, hydrogen and carbonaceous fine particles is thermally cracked, and the cracked product is cracked into gas, light oil, medium oil and cracked residue. The cracked residue is deasphalted to produce a deasphalted oil and a relatively asphaltene-rich hydrocarbon fraction, and the relatively asphaltene-rich hydrocarbon fraction is gasified in the presence of oxygen and steam. To produce a synthesis gas, from which carbonaceous particulates are separated, and wherein the separated particles are recycled to thermal cracking. The presence of hydrogen in the thermal cracking zone reduces the problems posed by the formation of carbonaceous products during thermal cracking and results in oils with high stability and low olefin content. In this known method, the material to be thermally cracked is heated indirectly to the cracking temperature, i.e. via the walls through which heat is conducted. A disadvantage of this method is that the oxidative deposits on the inner walls due to the mixture to be thermally cracked gradually accumulate, which reduces the operating time of the furnace in which the heating takes place. This disadvantage is particularly acute where high conversions of heavy hydrocarbons are intended. Another disadvantage is that metal and ash particles, which are normally present in synthesis gas, are not removed. As a result, metals and ash will be present in increasing concentrations.

The object of the invention is to avoid the disadvantage of indirect heating of the residual hydrocarbon oil to the cracking temperature.

Another object is to avoid high concentrations of metal and ash particles.

A further object is to use readily available forms of hydrogen.

Accordingly, the present invention provides a method for thermal cracking of residual hydrocarbon oil, comprising the following steps: Step 1 Residual hydrocarbon oil and synthesis gas are supplied to a thermal cracking zone. The synthesis gas has a temperature high enough to maintain the temperature of the thermal cracking zone in the range of 420 ° C. to 850 ° C. by direct heat exchange; Decomposes the product into (a) a gaseous fraction containing synthesis gas, (b) one or more hydrocarbon distillate fractions and (c) a cracking residue, step 3 cracking residue from step 2 The product is separated into one or more heavy hydrocarbon oils relatively poor in asphaltene and one or more heavy hydrocarbon oils relatively rich in asphaltenes; One or more heavy hydrocarbon oils I and gasified to produce a synthesis gas in the presence of carbon and steam, and applies the synthesis gas from step 5 step 4 as synthesis gas of step 1.

The residual hydrocarbon oil is contacted directly with the thermal synthesis gas in step 1, thus providing heat for thermal cracking and avoiding the disadvantage of indirect heating of the residual hydrocarbon oil to the cracking temperature. Efficient contacting is an important means for reducing the formation of carbonaceous products. Contacting can be effected efficiently by providing a high oil-to-gas interface to the thermal cracking zone, for example, using a spray reactor in which the residual hydrocarbon oil and the thermosynthetic waste are introduced separately.

The temperature in step 1 is an important process variable during thermal cracking. The desirable effect of thermal cracking, ie, reducing the molecular weight and viscosity of the residual hydrocarbon oil, results from large molecules having higher cracking rates than small molecules. From “Sachanen,“ Conversion of Petroleum ”, 1948, Chapter 3,
It is known that at lower temperatures, the difference in cracking rates between large and small molecules is greater, and thus the desired effect produced is greater. At very low temperatures, for example below 400 ° C., the cracking rate is reduced to uneconomically small values and considerable amounts of ethylenically unsaturated products are formed. Very high temperature ie 85
At temperatures above 0 ° C., large amounts of gas and carbonaceous products are formed, relatively small amounts of hydrocarbon distillate fractions are formed in step 2 and heavy hydrocarbons relatively poor in asphaltenes in step 3 Oil is produced in relatively small amounts. Produces relatively large amounts of heavy hydrocarbon oils which are relatively poor in distillate fractions in step 2 and asphaltenes in step 3 (furthermore, so that they have a considerably reduced content of ethylenically unsaturated products) Therefore, the temperature of the thermal cracking zone is preferably in the range from 420 ° C to 645 ° C, more preferably in the range from 460 ° C to 550 ° C.

Residual hydrocarbon oil and syngas are fed to a thermal cracking zone, where a reaction mixture is formed, and the reaction mixture is held for an average residence time. This average residence time is another important process variable during thermal cracking. Generally, the average residence time is set according to the temperature. The thermal cracking of step 1 is preferably carried out with an average residence time in the range from 1 second to 10 minutes, more preferably in the range from 10 seconds to 10 minutes. At a residence time of less than 1 second, thermal cracking does not proceed sufficiently, and at a residence time of more than 10 minutes, the amount of gas and carbonaceous products increases, and a relatively small amount of hydrocarbon distillate is produced in Step 2. Heavy hydrocarbon oils which are relatively low in asphaltene in step 3 are produced. The average residence time is defined herein as V: F, where "V" is the volume of the thermal cracking zone and "F" is the volume of residual hydrocarbon oil fed to this zone per unit time. .

The pressure in step 1 is preferably 2 to provide a high oil-to-gas interface in the thermal cracking zone and to increase the production of heavy hydrocarbon oils relatively low in asphaltenes in step 3. It is selected in the range from 5050 bar, especially from 3 to 10 bar.

Examples of residual hydrocarbon oils which can be used in step 1 of the process according to the invention include long residue, short residue, distillation of hydrocarbon mixtures produced by thermal cracking of hydrocarbon oils in the absence of added hydrogen. Residue obtained, as well as residual oil obtained from tar sands or shale oil. If desired, the residual hydrocarbon oil may be a heavy distillate fraction (eg, a circulating oil obtained by catalytic cracking of a hydrocarbon oil fraction) or a heavy carbon oil obtained by extraction from the residual hydrocarbon oil. It may be blended with hydrogen oil.

The cracked products from step 1 are separated in step 2 into a gaseous cut, one or more hydrocarbon distillate cuts and cracked residues. This can be done, for example, by removing gas from the top of the thermal cracking zone and cracking residue from the bottom. The gas taken from the top is
Distillation at atmospheric pressure allows (a) synthesis gas, hydrocarbons having from 1 to 4 carbon atoms per molecule and hydrogen sulfide (hydrocarbon fraction relatively rich in asphaltenes to be gasified in step 4) Contains sulfur)
, A (b) naphtha cut, (c) a kerosene cut, (d) a gas oil cut and (e) a small residue. This small amount of residue can be mixed with the decomposition residue obtained in step 2. Hydrogen sulfide can be removed from the gaseous cut by any suitable conventional technique. After this removal, the gaseous fraction can be separated into synthesis gas and hydrocarbons by conventional separation techniques. This synthesis gas can be reused in step 1 (after hydrogen enrichment, if desired) and / or used, for example, as a fuel gas or as a gas for driving a power generating turbine.

The separation residue from step 2 contains, inter alia, heavy hydrocarbon oils, asphaltenes, suspended carbonaceous particles and heavy metals (if heavy metals are present).

According to a preferred embodiment of the present invention, the cracked residue from step 2 is separated in step 3 by distillation at a pressure below atmospheric pressure from one or more heavy hydrocarbon distillates relatively asphaltene and asphaltene Is separated into heavy residual hydrocarbon oils, which are relatively rich in oil. The distillation is suitably a flash distillation, and can be performed in one or more columns or flash vessels.

According to another preferred embodiment of the present invention, the cracked residue from step 2 is contacted with an extractant in step 3 to compare the extract phase and asphaltenes containing heavy hydrocarbon oils relatively poor in asphaltenes. Produces an extraction residue consisting of highly enriched heavy hydrocarbon oils. The extractant is preferably an alkane or a mixture of alkanes, especially propane, butane, isobutane and / or pentane. Pentane is more preferred. Such extraction methods are well-known in the art. The extract phase and the extract residue, a heavy hydrocarbon oil relatively rich in asphaltenes, can be separated by sedimentation by gravity, and the cracked extract phase can be separated by distillation from heavy hydrocarbon oils relatively poor in asphaltenes and heavy hydrocarbon oils. It can be separated into extractants.

The relatively asphaltene-rich hydrocarbon fraction also contains suspended particles of carbonaceous products and heavy metals (if heavy metals are present) such as vanadium and nickel. This fraction is gasified in step 4 in the presence of oxygen and water vapor to produce a synthesis gas containing carbon monoxide and hydrogen as main components, the gasification being a partial oxidation. Thus, hydrogen is readily available and need not be separated from carbon monoxide. The synthesis gas contains particles of carbonaceous product, particles of ash, and usually particles of heavy metals.

The gasification in step 4 can be carried out, for example, with a weight ratio of oxygen to hydrocarbon fraction in the range of 0.5 to 1.5 and a weight ratio of steam to hydrocarbon fraction in the range of 0.2 to 1. Both of these weight ratios depend on the molecular composition of the fuel and the temperature at which gasification occurs. These weight ratios also determine the amount of carbonaceous product produced. The gasification can be carried out, for example, at a pressure in the range from 1 to 100 bar and a temperature in the range from 1000 ° C to 1600 ° C.

Preferably, the metal and ash particles present in the syngas from step 4 are removed before this gas is applied in step 5. Removal may be performed from the main component gas stream, but is suitably performed from its bypass stream. Suitably, the removal is performed at a temperature at which synthesis gas becomes available.

The metal and ash particles are preferably selectively from the syngas from step 4 (ie, selectively with respect to the particles of the carbonaceous product) before it is applied in step 5.
Removed. The advantage is that the particles of the carbonaceous product go into the relatively hydrocarbon rich asphaltenes separated in step 3 and are then gasified in step 4. It is a preferred feature of the present method that the carbonaceous product particles do not need to be disposed of as waste products. Such selective removal can be based on the size and density differences between the carbonaceous product particles and the metal and ash particles. Particles of the carbonaceous product usually have a relatively small size and relatively low density, while particles of metal and ash typically have a relatively large size and relatively high density. This separation can be performed, for example, by a cyclone separator. The metal and ash particles thus separated can be used for recovery of these metals.

The syngas should have a temperature high enough to maintain the temperature in the thermal cracking zone at a value in the range of 420 ° C to 820 ° C. The fact that excess heat is usually available in the syngas for this requirement is a preferred feature of the present invention. Therefore, the heat present in the synthesis gas from step 4 can usually be extracted from this gas (preferably by indirect heat exchange with a cooling medium, for example water).
This makes it possible to produce relatively high pressure steam and to control the temperature in the zone of thermal cracking. Instead, the syngas is split into two parts, one of which is used in Step 1 to maintain the temperature of the thermal cracking zone at a value in the range of 420 ° C to 850 ° C, and the other is used in other suitable applications. Used for For example,
This other part may be combusted in the power generating turbine.

The relatively poor asphaltene hydrocarbon fraction separated in step 3 can be used for any suitable application. For example, this fraction has a relatively low density, viscosity and Conradson carbon content and contains no or very low carbon particle content, making it very suitable as a commercial fuel formulation. . Instead, the fractions can be cracked jointly or hydrocracked to produce gasoline and kerosene fractions, or for thermal cracking into relatively light hydrocarbon distillate fractions. Can be recycled to the thermal cracking zone in step 1.

The present invention will be described in more detail with reference to the accompanying drawings. 1 and 2 are simplified flow diagrams of the method according to the invention, however, without auxiliary equipment such as heat exchangers and valves. FIG. 1 shows an embodiment in which the decomposition residue is distilled at a pressure lower than the atmospheric pressure, and FIG. 2 shows an embodiment in which the decomposition residue is deasphalted.

Referring to FIG. 1, heavy hydrocarbon oil is introduced into a thermal cracking device 3 via lines 1 and 2. Syngas is supplied to the thermal cracking device 3 via line 4 (step 1).

From the thermal cracking device 3, the gas phase and the decomposition residue
It is taken out via line 5 and line 6, respectively. The gas phase is introduced into distillation column 7 via line 5 where it is separated at atmospheric pressure into a synthesis gas containing top fraction, a full range naphtha fraction, a gas oil fraction and a bottom fraction, and from distillation column 7 respectively. It is taken out via line 8, line 9, line 10 and line 11 (step 2).

Cracking residue is introduced into the vacuum distillation column 13 via the line 6 and the line 12 where the vacuum top fraction, the one or more vacuum distillates and the bottom fraction containing asphaltenes at a pressure below atmospheric pressure And removed from the vacuum distillation column 13 via lines 14, 15 and 16, respectively (step 3). The top cut and distillate are substantially free of asphaltenes, and the bottom cut contains particles of carbonaceous product.

Asphaltene-containing fractions in line 16, pump 17
And via line 18 into a gasifier 19, to which oxygen and steam are supplied via line 20. The synthesis gas generated in the gasifier 19 is supplied to the line
It is taken out through 21 (step 4).

The synthesis gas is directed via line 21 to a separator 22, where metal and ash particles are selectively removed from the gas. Syngas substantially free of metal and ash particles, but still containing particles of carbonaceous product, is withdrawn from separator 22 via line 23 and introduced into waste heat boiler 24 where excess Heat is extracted from the syngas.
Syngas having reduced temperature is withdrawn from waste heat boiler 24 via line 4 and introduced into thermal cracking device 3 as described above (step 5).

Metal and ash particles removed from the syngas in separator 22 are withdrawn via line 25. Water line 26
Is supplied to the waste heat boiler 24,
Removed via 27.

Vacuum distillate, which is conducted through line 15, is in this case partly conducted via line 28 to a place for use outside the process and partly recirculated via line 29 to line 2. To increase the production of the full range naphtha and gas oil fractions via lines 9 and 10, respectively. Instead,
All of the vacuum distillate from line 15 may be removed via line 28. It is usually preferred that the latter approach is possible.

The bottom fraction guided via line 11 is introduced into line 12 via pump 30 and line 31.

In FIG. 1 and FIG. 2, reference numbers for corresponding parts are the same.

With reference to FIG. 2, the cracked residue from the thermal cracking unit 3 is introduced via line 6 to a solvent deasphalting unit 50, where deasphalted oil substantially free of carbonaceous product particles, and asphaltene and carbonaceous material. The product is broken down into fractions containing particles and removed from the apparatus 50 via line 15 and line 16 respectively (step 3),
The carbonaceous product thus originates from the gasifier 19 and the thermal cracking unit 3.

The deasphalted oil withdrawn via line 15 is directed, in part, through line 28 to a location for use outside of the process, and is partially recycled through line 29 to line 2 to provide a full range naphtha fraction. And the production of the gas oil fraction is increased via lines 9 and 10, respectively. Instead, line 15
All of the deasphalted oil from the system may be removed via line 28. It is usually preferred that the latter approach is possible.

Example 1 This example was performed with respect to FIG. The heavy hydrocarbon oil guided through line 1 was a short residue having the following properties: Density (25 ° C / 25 ° C) 1.028 Viscosity (150 ° C) 154 cS Initial boiling point (° C) 520 Vanadium content (ppm) 135.8 nickel content (ppm) 43.3 sulfur content (wt%) 5.30 Conradson carbon (wt%) 21.7 C ₅ ~ asphaltenes (wt%) 19.9 abbreviated "ppm" is a part per million parts by weight means. The thermal cracking device 3 was a cylindrical vessel, operated at a temperature of 475 ° C., a pressure of 6.0 bar and an average residence time of 3 minutes. The gasifier 19 is operated at a temperature of 1400 ° C., a pressure of 30 bar and a residence time of 5 seconds, and the distillation column 13 has a pressure of 0.1 bar.
Operated at a pressure of 013 bar. High pressure steam was withdrawn via line 27.

The following overall material balance was observed: Material balance relates to thermal cracking down device 3 were as follows: material balance relates to input output line kg / h Line kg / h 4 112.5 5 142.0 2 125.0 6 95.5 237.5 237.5 vacuum distillation column 13, as follows there were: the nature of the fraction containing asphaltenes in nature and line 16 of the distillate of the vacuum flash in input output line kg / h line kg / h 12 95.5 14 negligible 15 48.25 16 47.25 95.5 95.5 line 28, the following Is as follows: The vacuum flash distillate contained no carbonaceous product particles. The composition of the fraction containing asphaltenes excludes carbonaceous product particles.

The gas in line 4 had the following composition (at 20 ° C.) in mole%, excluding particles of carbonaceous product: CO 46.6 CO ₂ 3.4 H ₂ S 1.4 H ₂ 41.5 H ₂ O 6.5 N ₂ 0.6 Example 2 This example was performed with respect to FIG. The heavy hydrocarbon oil guided through line 1 was the same short residue used in Example 1. The thermal cracking unit 3 was operated at a temperature of 475 ° C., a pressure of 6.0 bar and a cold oil residence time of 3 minutes. Gasifier 19 is 1400
It was operated at a temperature of ° C., a pressure of 30 bar and a residence time of 5 seconds. The extraction column or solvent deasphalting device 50 was a rotary plate contactor and was operated isothermally at a temperature of 185 ° C. and a pressure of 40 bar and using n-pentane as the extractant. An extractant to feed weight ratio of 2.0 was applied, using a rotation speed of 100 revolutions per minute.

The following overall material balance was observed: Material balance relates to thermal cracker 3 was as follows: material balance relates to input output line kg / h Line kg / h 4 63.3 5 97.8 2 125.0 6 95.5 193.3 193.3 solvent deasphalting unit 50 was as follows were: oN output line kg / h line kg / h 12 95.5 15 66.8 16 28.7 95.5 95.5 gas in line 4, have the following composition (at 20 ° C.) in mol% to the exclusion of the particles of carbonaceous products CO 48.2 CO ₂ 3.1 H ₂ S 1.6 H ₂ 40.9 H ₂ O 6.0 N ₂ 0.2 Deasphalted oil properties and line at line 28
The properties of the asphaltene-containing fraction in 16 are as follows: The composition of the fraction containing asphaltenes excludes carbonaceous product particles. The deasphalted oil is
It did not contain particles of carbonaceous product.

[Brief description of the drawings]

1 and 2 are simplified flowcharts of the method according to the invention. 3 ... thermal cracking device, 7 ... distillation column 13 ... vacuum distillation column, 17 ... pump 19 ... gasifier, 22 ... separator 3 24 ... waste heat boiler, 30 ... pump 50 ... Solvent deasphalting equipment

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Jean-Jiant Jacques Henri Emanyuel Le Del Amico 76530 Grand Coulon, France, Rout de Caen (No address)

Claims (11)

(57) [Claims] 1. A method for thermally cracking residual hydrocarbon oil, comprising the steps of: Step 1: supplying residual hydrocarbon oil and synthesis gas to a thermal cracking zone, wherein the synthesis gas is thermally cracked. Having a temperature high enough to maintain the temperature of the zone at a value in the range of 420 ° C. to 850 ° C. by direct heat exchange; Step 2 decomposing the decomposition product from Step 1 into a gas containing (a) a synthesis gas; Step (b) one or more hydrocarbon distillate fractions and (c) cracking residue; step 3 cracking residue from step 2 is one or more relatively low in asphaltenes The above-mentioned heavy hydrocarbon oil and one or more heavy hydrocarbon oils relatively rich in asphaltenes are separated into one or more heavy hydrocarbon oils. Step 4 One or more heavy carbon oils relatively rich in asphaltenes from Step 3 Hydrogen oil Gasified to produce a synthesis gas in the presence of Motooyobi steam, and applies the synthesis gas from step 5 step 4 as synthesis gas of step 1. 2. The method according to claim 1, wherein the thermal cracking in step 1 is performed at a temperature in the range from 420 ° C. to 645 ° C. 3. The method according to claim 2, wherein the thermal cracking in step 1 is performed at a temperature in the range of 460 ° C. to 550 ° C. 4. The method according to claim 1, wherein step 1 is carried out at a pressure in the range from 3 to 10 bar. 5. The heat cracking in step 1 for 1 second to
5. The method according to claim 1, wherein the method is carried out with an average residence time in the range of 10 minutes. 6. The method of claim 5, wherein the thermal cracking in step 1 is performed with an average residence time in the range of 10 seconds to 10 minutes. 7. The process according to claim 1, wherein the heat present in the synthesis gas from step 4 is removed by indirect heat exchange with a cooling medium before applying this gas in step 5. Method. 8. The process of claim 1 wherein metal and ash particles present in the syngas from step 4 are selectively removed relative to carbonaceous product particles prior to applying the gas in step 5. Item 8. The method according to any one of Items 7 to 7. 9. The cracked residue from step 2 is distilled in step 3 at a pressure less than atmospheric pressure, and one or more heavy hydrocarbon oil distillates relatively asphaltene and relatively rich in asphaltenes 9. The process according to claim 1, wherein the process separates into heavy residual hydrocarbon oils. 10. The cracked residue from step 2 is contacted with an extractant in step 3 to produce an extract phase containing a heavy hydrocarbon oil relatively poor in asphaltenes and a heavy hydrocarbon oil relatively rich in asphaltenes. A process according to any one of the preceding claims, wherein an extraction residue consisting of 11. The method according to claim 10, wherein the extractant is propane, butane, isobutane and / or pentane.